1. Field of the Invention
The present invention relates generally to a fire alarm system, a fire sensor, a fire receiver, and a repeater, and more particularly to a fire alarm system which includes fire sensors provided at the predetermined places within a building, and a fire receiver for receiving a fire alarm signal from the fire sensors.
2. Description of the Related Art
FIG. 46 shows a proprietary type fire alarm system (hereinafter referred to as a P-type fire alarm system). This fire alarm system includes a fire receiver 2, which has a plurality of sensor lines L1 to Ln. Each of the sensor lines L1 to Ln are connected with a great number of fire sensors 1. The operations of the fire sensors 1 are collectively monitored for each sensor line by the fire receiver 2.
The range to be monitored by the P-type fire alarm system is not the unit of a single fire sensor 1 but the unit of a sensor line (L1 to Ln) to which a plurality of fire sensors 1 are connected. Therefore, when a certain fire sensor 1 is operated, an area allocated to a sensor line (e.g., line L1) including the operated fire sensor 1 is specified as the place of the occurrence of a fire by the fire receiver 2.
However, it is desirable that the place of the occurrence of a fire be pinpointed. In view of that point, the present applicant has proposed a fire alarm system (Japanese Patent Application No. HEI 11-366915 (Dec. 24, 1999)). The fire alarm system includes a receiver (equivalent to a fire sensor), and a plurality of fire sensors connected to a sensor line. In the fire alarm system, a fire information signal from a fire sensor is received in the unit of a line (equivalent to L1 to Ln). The fire alarm system further includes a retrieval section and a response section. The retrieval section is provided on the side of the receiver. When fire information is sensed, the retrieval section sends a retrieval signal on the line from which the fire information was issued, and retrieves the fire sensor which issued the fire information. The response section is provided for each of the fire sensors. The response section sends back a retrieval response signal when it recognizes the above-described retrieval signal at the time of a fire.
The fire receiver issues an alarm, if it receives a fire information signal from a fire sensor. At the same time, the fire receiver sends out a retrieval signal on the line from which fire information was issued. On the other hand, the fire sensor which issued fire information sends back a retrieval response signal, if it receives the retrieval signal from the fire receiver. In this manner, a fire alarm system of a question/answer type is constructed.
Therefore, since the fire sensor that answered can be specified by the fire receiver, the place of a fire can be pinpointed in the unit of a fire sensor. As a result, the accuracy of a fire alarm can be considerably enhanced.
In the above-described fire alarm system, the fire receiver includes the above-described retrieval section, and the fire sensor includes the above-described response section. Between the retrieval section and the response section, a question/answer system is constructed. A question and an answer are performed with a single transmission line in which transmission and reception are switched. Because of this, if the line number n is increased, the time for specifying the place of a fire will be increased in proportion to the line number n.
In addition, in such a fire alarm system, sensors must have a dedicated line that can answer the signal from the transmitter in order to specify a sensor that issued an alarm. Therefore, the fire alarm system has the disadvantage that it cannot utilize the existing systems.
FIG. 47A shows a fire alarm panel provided in public facilities such as a school, etc. The fire alarm panel 101 is attached, for example, to the wall of a building and includes a bell 102, a red display light 103, and a transmitter 104.
The transmitter 104 includes a circular main body 105 painted red, and a nameplate 106 with a printed or carved suitable character string indicating a use (e.g., a fire alarm), mounted on the main body 105. The transmitter 104 further includes a circular hole 108, which is formed near the central portion of the circular main body 105 and protected with a transparent plastic window 107. Within the circular hole 108, there are provided a push-button switch 109 and an operation confirming light 110.
FIG. 47B shows the circuit diagram of the transmitter 104. The push-button switch 109 consists of two contacts a and b. The first contact a is positioned between an L line and a C line, while the second contact b is positioned between an A line and the C line through the operation confirming light 110. The A line and C line are drawn from a transmitter 111 to all monitoring areas.
In the above-described construction, if the plastic window 107 is destroyed and the push-button switch 109 is depressed, the bell 102 rings and the two contacts a and b are closed. That is, the L and C lines are short-circuited through the first contact a. At the same time, the A and C lines are short-circuited through the second contact b. If the short-circuited state (between the L and C lines) is transmitted to the transmitter 111, a predetermined DC current is applied from the transmitter 111 on the A line. Since the predetermined DC current flows in the order of A line->operation confirming light 110->contact b->C line, the operation confirming light 110 provided in the transmitter 104 is lit. With the lighting, it can be confirmed that the receiver 111 has received the depression of the push-button switch 109. The predetermined DC current, for lighting the operation confirming light 110, will hereinafter be referred to as answer current. In FIG. 47C, the letter “i” in the Li line represents the number of a monitoring area. Therefore, the Li line represents an L line connected to the ith monitoring area. For example, if a transmitter 104 belongs to the first monitoring area, the first contact a of the transmitter 104 is positioned between the L1 line and the C line.
Although such a transmitter 104 is used to inform the surrounding people of the occurrence of a fire, the use of the transmitter 104 is not limited to this. For instance, in the case of an abnormal situation such as an assault by a ruffian, there are cases where the nearby transmitter 104 is operated to ring the bell 102, repulse a ruffian, and ask the surrounding people for help. In addition, when a suspicious person is found in schools, etc., the above-described transmitter can be utilized to quickly inform the surrounding people of the suspicious person.
However, the above-described transmitter 104 is used for issuing an alarm with the ring of a bell. Therefore, in a large building (e.g., a school) where a great number of transmitters 104 are disposed, it is fairly difficult to specify the transmitter 104 which is issuing an alarm, and consequently, there is a problem that guards or teachers cannot rush to the place of an abnormal situation.
Note that a large building is equipped with a system in which fire-information signals from a great number of transmitters are collectively monitored with a receiver (e.g., a P-type fire receiver). In this system, as shown in FIG. 47C, signals from a great number of transmitters 104 provided at the predetermined places within a building are transmitted to the receiver 111 through a dedicated reception line (which consists of Li and C lines (L-C line)) for each monitoring area. The receiver 111 transmits a confirmation signal (answer signal), which indicates that an alarm was received, to the transmitter 104 through a confirmation line (which consists of A and C lines (A-C line)). As a result, the operation confirming light 110 of the transmitter 104 is lit. In this manner, the person who operated the transmitter 104 is informed of the confirmation of reception by the receiver 111. However, since a great number of transmitters 104 are connected for each monitoring area, it is extremely difficult for the receiver 111 to specify the transmitter 104 in one monitoring area which issued fire information, and consequently, there is a problem that guards or teachers cannot rush to the place of an abnormal situation.